Radiation therapy is an important treatment modality of cancer. However, therapeutic management may be limited by the inherent relative resistance of some cancers to the cytotoxic effects of ionizing radiation. Recently, several lines of investigation have coalesced to demonstrate a link between certain oncogenes (ras, raf, cot, mos, myc), growth factors (PDGF, FGF) and the phenomenon of cellular resistance to ionizing radiation.
It was previously reported that expression of antisense c-raf-1 cDNA results in reduced expression (RNA) of c-raf-1 gene, a cause of delayed tumor growth in athymic mice and in enhanced radiation sensitivity of relatively radioresistant laryngeal squamous carcinoma cells, SQ-20B (Kasid et al., Science 243:1354-1356, 1989).